1. Field of the Invention
The invention relates to a hypodermic syringe head with a tamper-evident closure for a syringe barrel, which has a barrel neck that is provided with an axial fluid outlet conduit and a circumferential bead for anchoring the hypodermic syringe head, having an injection cannula, which is mounted in a cannula carrier from which it protrudes on both axial ends and which is disposed in a cannula carrier guide so as to be movable relative thereto, and a cannula guard cap which is adjoined, via a rated breaking point, by an anchoring element that solidly holds the cannula carrier guide and can be affixed with elastic deformation to the circumferential bead of the barrel neck, and the cannula guard cap has axially extending ribs on its inside circumference which engage corresponding ribs of the cannula carrier for rotationally driving it.
2. Description of the Prior Art
One such hypodermic syringe head is intended to close so-called ready-to-use syringes, that is, syringes that are filled with a liquid medication and packed in sterile form, with an injection cannula, and are sold ready for use. It is understood that these ready-to-use syringes are provided with a tamper-evident closure, which makes it possible to see whether the syringe is still filled with the original contents and is still sterile. The hypodermic syringe head is intended to protect the cannula adequately so that upon final mounting of the syringe head on the syringe barrel, no damage to or contamination of the cannula can occur. For the sake of mass production, a simple construction of the hypodermic syringe is also necessary.
In one hypodermic syringe head of the type defined at the outset above, the problem also arises that if the guard cap is unintentionally twisted the wrong direction relative to the anchoring element, the rated breaking point will indeed break but the cannula will now be forced through the sealing disk and put into communication with the medication contained in the syringe barrel.